Recently, organic polymer actuators have been developed.
PTL 1 discloses a conductive polymer actuator including a working electrode, a counter electrode disposed opposite the working electrode, and an interlayer film in contact with the two electrodes, all of which are immersed in an electrolytic solution. A voltage applied across the working electrode and the counter electrode causes the working electrode to extend and contract in the electrolytic solution.
According to Example 2 of PTL 1, the working electrode is a cylindrical gold-polypyrrole composite, and the interlayer film is a porous polyvinyl alcohol film formed by electrospinning (electrospun sheet). The outer surface of the cylindrical working electrode is covered with the electrospun sheet and is further covered with the polypyrrole counter electrode to form an electrode assembly. The electrode assembly is sealed in a glass tube by pouring an electrolytic solution, thus fabricating an actuator.
An extensible actuator, such as the one disclosed in PTL 1, needs to be formed of a material that can be flexibly extended and contracted because the entire actuator extends and contracts in the longitudinal direction. That is, an intermediate layer formed of a more extensible and flexible film provides better deformation response characteristics, although it has a lower mechanical strength.
Accordingly, it is difficult for the actuator itself to achieve sufficient generative force, and it is therefore difficult for the actuator to simultaneously achieve better deformation response characteristics and larger generative force.
PTL 2, on the other hand, discloses a bending actuator including a cation exchange film as an intermediate layer between a pair of electrodes. A potential difference applied across the cation exchange film causes it to curve or bend. However, the cation exchange film itself does not have good deformation response characteristics.